Flute casts and related structures on moulded silt injection surfaces in continental sandstone of the Boss Point Formation: southeastern New Brunswick, Canada

Abstract

Canada 3 E3L 4L5Flute, load and groove cases occur widely at the sharp Interfaces of slltstone diapirs, injection lenses, and pods In fluvial sandstone of the Boss Point Formation of southeastern New Brunswick.These concordant and discordant injection features range from approximately 20 centimetres (pods) to many metres (injection lenses) in diameter. They are confined to "brecciform intervals" that can be traced along strike and dip for a hundred metres or more.The flute, load and groove casts on the injection surfaces, have evidently not been formed by any primary sedimentary process but are the result of liquefaction, 9ediment injection and flow moulding during postdepositional compaction of the strata. The term "rheoplasis" la proposed to denote this process, and the general term "rheoplastic structures" or "rheoplasts" refers to the range of sole-marking like structures formed as a result of this process.The realization that flute casts can form as a result of post-deposltional processes is of great significance In the classification of sedimentary structures and the' interpretation of deposltional environments and attendant sedimentary processes.Au sud-est du Nouveau-Brunswick, dans les grSs fluviatiles de la formation de Boss Point, on peut voir de nombreux exemples de flutes, empreintes de charge et cannelures aux interfaces distincts de diapirs de siltstone, de lentilles d'injection, de mottes et de loupes. Ces elements d'injection sont concordants ou discordants et possedent un diametre allant de 20 cm (pour les loupes) Jusqu'S plusieurs metres (pour les lentilles d'injection). lis sont egalemenr. restreints 3 des "intervalles brechiques" que l'on peut suivre sur des centaines de metres et plus, le long de la direction et du pendage de la stratification.Les flutes, cannelures et empreintes de charge que l'on retrouve sur les surfaces d'injection ne resultent evidemroent pas d'un processus sedimentaire primaire mais plutot de la liquefaction, de 1'injection du sediment et du moulage des coulees durant la compaction apres la deposition de la strate. Pour marquer ce procede, on propose le terme "rheoplasie" alors que le terme plus global "structures rheoplastiques" (ou "rheoplastes") s'applique aux empreintes de toutes sortes qui resultent de ce meme procede et que l'on retrouve sur la surface inferieure d'une strate.La classification des structures sedimentaires ainsi que 1'interpretation des environnements de deposition et des procedes sedimentaires connexes seront grandement influencees par le fait que des flutes peuvent resulter d'un procede post-depositionnel.[Traduit par le journal]

Sediment Flow and Deformation (SFD) Layers: Evidence for Intrastratal Flow in Laminated Muddy Sediments of the Triassic Osawa Formation, Northeast Japan

“…Peterson (1968), van de Poll and Patel (1981), van de Poll and Plint (1983), Plint et al (1983), Keighley and Pickerill (1994), and Aalt (1996) reported many ''flow structures,'' especially flute-like or ripple-like marks developed at the interface of injected mud and hosted sand or of injected sand and hosted mud. Unfortunately, no contact plane can be observed in plan view for the SFD layer.…”

An ornamented mudstone cavity, Boss Point Formation, Sackville, New Brunswick, Canada: evidence for mud intrusion and rheoplasis

“…Rejection of the previous three hypotheses, as unsatisfactory because they fail to account for all features, leads to Hypothesis 4; that the cavity and the associated structures are not primary but are entirely the result of secondary processes related to diapirrc intrusion. This hypothesis was first suggested by van de Poll & Patel (1981) to account for similar ornamentation on mudstone bodies within brecciforms in the Boss Point Formation, at Alma and Cape Enrage some 45 km southwest of Sackville. Of particular interest within the context of the present discussion are the well-developed, comet-shaped flute moulds on the wall of a large mudstone cavity at Cape Enrage in a brecciform containing mud bodies ranging from a few centimetres to several metres in diameter (van de Poll & Patel, 1981, Figs 9 & lo).…”

“…(4) It is entirely secondary in origin, being due to diapiric intrusion from the mudstone bed below ; the ornamentation was formed by rheoplasis (van de Poll & Patel, 1981), as a result of the actual process of intrusion when both the mud and host sand were in a semi-fluid or liquefied state.…”

“…The origin of mudstone bodies in the Boss Point Formation that filled cavities prior to selective weathering and erosion of the mudstone has been discussed at some length with opposing views by van de Poll & Patel (1981 and Plint (1986Plint ( , 1989. Though not dismissing sediment intrusion and rheoplasis as a valid process, Plint (1989) stated that the concept does not apply to the cavities in the Pennsylvanian of southern New Brunswick.…”

Erosional marks on consolidated banks and slump blocks in the Rupen River, north‐west India

“…The steeply inclined mudstone surfaces were interpreted by these authors as original channel margins, and the detached mudstone masses as slump blocks emplaced into the channels through bank collapse. However, other workers have attributed the structures to 'rheoplasis' (flow-molding), a process of simultaneous loading and differential flow across a sandmud interface during early burial [van de Poll & Patel, 1981, 1989, 1990Keighley & Pickerill, 1994, 1996. The detached mudstone masses have been described as mud diapirs.…”